2708 EPROM Dumper

[Andrea “Mancausoft” Milazzo] has been restoring old equipment which often contain EPROM chips. He thought he was all set with an EPROM reader which easily dumped the data from 2716 chips and a few others. But he found that the hardware was unable to read 2708 and 2704 chips. His solution was to build a PIC-based EPROM dumper.

You may remember from some of our recent features that these chips are something of a ticking clock. They store program code and other information vital to the functioning of old hardware. Since they’re erased with UV light, years of exposure to ambient light can zap some of the data.

The specs needed to read a chip of this type are rather rudimentary. There are ten address pins and eight data pins. [Andrea] also needed a way to get data from the microcontroller to a computer for backup. He uses two more pins for this purpose, bringing the I/O count to 20. He went with  PIC 18F4610 and built the rest of the reader around it.

4 thoughts on “2708 EPROM Dumper

  1. Yeah… you’d really have thought that someone would’ve said “Hmmm… we’d like to keep this… maybe we should put some electrical tape over the window.” But I’ve just about never seen that :/

    1. I don’t think I’ve ever seen an EPROM in use without a sticker over the window. I’ve taken quite a few out of some old equipment too. I mean some are just paper stickers, but it’s way better than nothing.

  2. I’m late to the party but I’ve a couple of concerns with this:
    Theres no mention of PSU rail sequencing, if -5 (VBB) is not applied first and removed last, the 2708 can be destroyed.
    Programming isnt a single-shot thing like the 2716 upwards – the eprom is cycled through all 1024 addresses fifty times, with a 1ms programming pulse at each write, ie cycling through the addresses, each byte gets a 1ms hit, then the whole 1024-address cycle is repeated 50 times (see AMD, Intel, Motorola datasheets)

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